In various technical contexts there is a need for correct alignment of various components in relation to each other. In connection with the operation of large machines for example ventilation devices, pumps and similar plants the output power from a driving unit (e.g. a motor) is transmitted to a driven unit (e.g. a pump). This takes place via a rotational movement of the output shaft in the driving unit which transmits power to an input shaft in the driven unit.
In the operation of large motors, pumps and the like it is extremely important that the output shaft of the driven unit be correctly aligned relative to the input shaft of the driven unit. In this way, the output power from the driving unit can be transmitted optimally to the driven unit. Any misalignment of the two shafts in relation to each other can result in poor efficiency and increased risk of wear and damage to the various component parts.
Within this technical area there is therefore a need for correct and exact alignment of the output shaft in relation to the input shaft. In this context it can be noted that the two shafts can have alignment errors which are essentially of two different types. Most specifically, the shafts can be positioned so that they are placed at a relative angle to each other, corresponding to a horizontal or vertical angular error, or they can be positioned so that they are displaced in parallel to each other. The latter case corresponds to a situation where the shafts are placed in parallel to each other but somewhat displaced laterally relative to each other. This is usually called a horizontal or vertical offset error.
If these errors exceed predetermined threshold values, it can be assumed that the shafts are misaligned relative to each other. In such a situation, an operator can correct this by mechanically adjusting the physical position of one of the units or both of the units to eliminate the misalignment. Usually the position of one of the shafts is taken as a reference against which the other shaft is aligned.
Consequently, within the technical area in question, there is a need for systems and methods for correct alignment of various types of components including rotating shafts. Such systems and methods can be used for motors, pumps, ventilation systems, generators, paper making machines and in various other areas. In particular, these types of systems for alignment can be used in applications involving shafts rotating at high speed or in technical areas involving expensive and sensitive equipment where there is a great need to minimize unnecessary wear and the risk of breakdowns as a result of incorrect alignment of the shafts.
In the prior art it can be seen that a first shaft and a second shaft can be aligned by using an arrangement comprising a detector unit mounted on the first shaft and an additional detector unit mounted on the second shaft. Such an arrangement is shown in U.S. Pat. No. 4,518,855, which describes a first measuring device which is mounted on a first shaft and a second measuring device mounted on a second shaft. The first measuring device is provided with a first light source which is directed towards the second measuring device, while the second measuring device is provided with a second light source which is directed towards the first measuring device. The light sources are suitably laser light sources. The respective measuring device is disposed to detect the position of the light beam coming from the opposite device. During the measuring procedure, the shafts must rotate, in accordance with this known technology, so that the relative movements of the shafts at the various rotational positions can be detected. The information on the relative movement when measuring at various rotational positions provides information on the change of position of the respective shaft. This provides information on any misalignment of the two shafts.
U.S. Pat. No. 5,077,905 shows a device for alignment of two rotating shafts with the aid of measuring devices which are based on laser light sources and are disposed in connection with the respective rotating shaft.
Despite the fact that there are previously known devices and methods for alignment of rotating shafts, there is a continued need for improvement, particularly for achieving, if possible, an ever more precise measuring procedure which is simply implemented and at low cost.
The above type of measuring equipment is intended to be used when the relevant machines are standing still, i.e. when they are relatively cold and not in use for the moment.
It should however be noted that for many applications, the alignment between a motor and a pump can be changed when these machines are started and driven and gradually become warmed-up, i.e. they go from a cold and shut-off state to a state corresponding to normal operation. The alignment can for example vary depending on the operating temperature of the machines. The alignment can also vary depending on changes in the operating pressure (if the alignment is performed on a pump or a compressor). Furthermore, pipe load on the shafts can cause changes in the alignment between the cold and warm operating states.
The change in the alignment between a cold and a warm operating state can also be affected if the relevant machines are driven in parallel, or if changes in electric load or rotational forces occur during operation.
Thus there are thermal factors and other parameters which affect the alignment of the machines. As was described above, there is in particular a problem that correct alignment of a machine standing still does not necessarily correspond to a correct alignment of the same machine when it is in operation. This means that it will be necessary to perform some corrections to compensate for the fact that changes in alignment will occur between a cold and a warm state.
A previously known system for measuring the distance in alignment from a cold operating state to a warm operating state is manufactured by the company Prüftechnik and comprises two units made of combined transmitters and detectors intended to be mounted on a first stationary machine, suitably on a bearing housing of said first machine. The transmitters comprise laser light sources. Cooperating prisms are mounted on a second, portable machine which is intended to be adjusted so that corrected alignment is obtained.
Another known system is shown in U.S. Pat. No. 7,312,871, where a special fixture for rotation makes possible measurement of the difference in alignment between two operating states, both horizontally and vertically with a single-axis measuring system.